California sea lions get sick and aggressive toward humans after ingesting high levels of domoic acid, a neurotoxin found in algae blooms. In just three to four weeks, the Marine Mammal Care Center, a nonprofit rescue organization in Los Angeles County, received more than 20 reports of the creatures biting beachgoers, writes Rachel Barnes for Patch.com.
“It changes their brain chemistry, and when domoic acid concentrations are high, sea lions behave markedly,” says John Warner, the center’s executive director, in an NBC News report by Doha Madani “They become symptomatic in ways that are just unpredictable in terms of their behavior — aggression that we don’t normally see.”
Sea Lions Super Aggressive in California
Domoic acid enters the food chain when fish consume toxic algae known as Pseudo-nitzschia. The acid then builds up in larger sea creatures as they devour large numbers of fish. Since the bloom began in late May, many sick sea lions and dolphins have washed ashore in California, putting a strain on local teams responding to stranding activities.
The Channel Islands Marine and Wildlife Institute, which serves Santa Barbara and Ventura counties just north of Los Angeles, received more than 200 calls a day in June about animals in distress, BBC News’ Madeline Halpert reports. The company’s co-founder and CEO, Ruth Dover, tells CNN’s Rachel Ramirez that rescuers are “physically exhausted and emotionally tired” from the constant movement of strandings.
“We thought last year’s event that hit Santa Barbara and Ventura was tragic, but this year’s event is even more terrible,” Dover tells the paper. “Our beautiful beaches are littered with sick, dead, and deceased sea lions and dolphins.”
Domoic acid can kill or impair a variety of mammals, sea life, and even birds. In 1961, a Pseudo-nitzschia bloom caused strange behaviour in masses of seabirds in coastal communities around Monterey Bay. This event may also have inspired Alfred Hitchcock’s 1963 film The Birds, although, at the time, the cause of the birds’ erratic behaviour was unknown.
People can also become ill from consuming fish contaminated with domoic acid, although commercially purchased seafood is tested for the toxin, according to the California Department of Public Health (CDPH). Domoic acid poisoning, also known as amnesic shellfish poisoning, can appear anytime between 30 minutes and 24 hours after consuming poisonous fish. Symptoms include vomiting, headaches, and dizziness in mild cases, or seizures, confusion, coma, or death in severe cases, according to the department. In mid-June, CDPH issued a health advisory against eating mussels, clams, or scallops harvested for sport in Santa Barbara County.
Harmful algal blooms (HABs) frequently occur in warm or nutrient-rich waters. Many blooms are linked to excessive levels of phosphorus or nitrogen from fertilizers and sewage runoff.
Over the past 15 to 20 years, Pseudo-nitzschia blooms in California have increasingly threatened local flora, fauna, and fisheries. Those blooms tend to worsen in El Niño years when prolonged rainfall causes increased runoff — and by early June, meteorologists say, El Niño is already here.
Climate change may also make blooms more common and severe. This algae bloom appears to be due to wind-driven vitamin blooms in the water, which fuel algae growth, according to a Facebook post from NOAA Fisheries West Coast.
Professionals warn against approaching animals with symptoms of domoic acid poisoning, which, in the case of sea lions, consists of unusual head movements from side to side or holding their heads extended back.
But Warner tells NBC that people should not scare the animals. “Sea lions, as you know, are the ubiquitous ocean nature of California … that humans love. “And it’s not always them,” Warner explains in the handout. “I don’t want humans to see sea lions as Jaws … This isn’t about sea lions waking up one day sinisterly turned into man-biting beasts. I don’t want people to be afraid of those animals in the future. That’s a very sad situation.”